1. The Field of the Invention
The present invention relates to safety restraint devices for vehicles. More specifically, the present invention relates to hidden seams designed to permit airbag deployment without any evidence of the seam visible to a user.
2. The Relevant Technology
The inclusion of inflatable safety restraint devices, or airbags, is now a legal requirement for many new vehicles. Airbags are typically installed in the steering wheel and in the dashboard on the passenger side of a car. In the event of an accident, an accelerometer within the vehicle measures the abnormal deceleration and triggers the ignition of an explosive charge. Expanding gases from the charge fill the airbags, which immediately inflate in front of the driver and passenger to protect them from impact against the windshield.
During normal operation, the airbags are stowed behind covers to protect them from tampering and provide a more attractive interior facade for the vehicle. Seams, or deliberately weakened portions of the cover material, are included in the covers to ensure that the airbags deploy properly. Seams are necessary because, if the entire cover is made uniformly strong, random factors, such as manufacturing defects, in the cover will determine where the airbag emerges. It is necessary to ensure that deployment occurs at the proper location and time. Otherwise, a driver or passenger may not receive protection from the airbags, or may even be injured by improperly inflating airbags.
A seam may be a gap in the cover, held shut by threads, adhesives, etc. In the alternative, a seam may be constitute a line across the cover in which the material of the cover is formed thinner. In any case, the seam creates an inwardly-sloping region on the airbag cover. The seam may be on the inside of the cover, facing the airbag, or on the outside. Some covers include an outer layer of attractive material, such as leather, vinyl, or another plastic, that matches the remainder of the vehicle's interior. This layer also serves to cover the seam and hide it from view.
Other covers are made through “single-shot” construction, i.e., a manufacturing process in which only one single material is used. No cover layer is then used; rather, the surface facing the vehicle interior is made into a cosmetic surface through shaping and texturing. Styling lines are then typically molded into the cosmetic surface to obscure the underlying seam.
However, prior art seams typically have at least one long, straight section. Because of manufacturing methods currently used to attach the outer layer, the outer layer, if used, typically form-fits to the seam, creating an indentation in the outer layer over the seam. If no outer layer is used, a similar problem results because the styling line does not effectively fool anyone, and the styling line itself may be unsightly. If the styling line is omitted, a user may then “read through” the cosmetic surface and perceive the seam. Read through occurs because deformation of the material around the seam creates a visible indentation on the cosmetic surface. In many cases, the material of the seam is so thin that it is translucent to a user, who may then look through the cosmetic surface to perceive the seam or even the airbag inside the cover.
Consequently, nearly every vehicle with an airbag has a straight indentation or styling line in the interior finish. Since most airbags are placed at a location where they can protect a user from frontal impact, this indentation is nearly always directly in front of a person, in plain view. For this reason, the steering wheel and the passenger side dashboard of many vehicles prominently display a straight indentation or styling line covering the airbag.
The visible seam is problematic for a number of reasons. It may upset the design scheme of the interior material of the vehicle. Many modern vehicles utilize a smooth interior design that may be disrupted by the appearance of a seam in the middle of a panel. An automobile manufacturer may wish to employ curvilinear patterns on the interior finish of the vehicle. When combined with the straight indentations formed by prior art seams, however, such curvilinear patterns may appear incongruous and distracting.
Furthermore, a visible seam invites tampering by curious children and others. The seam is designed to yield to opening force, so it may be fairly easily broken to expose the airbag. If the airbag is tampered with, the owner may have to replace it, or may even be injured if it fails to deploy in the event of an accident. Even if no break is formed in the seam, the surface of the outer layer may be ruined by constant picking, poking, and scratching.
Moreover, another danger is present in vehicles in which interior airbag seams are visible. Some people form a habit of resting their hands in a certain fixed position on a surface, particularly over an irregularity such as a ridge, bump, or seam. For example, a driver may, while driving, subconsciously rub his or her fingers along the seam. Besides damage to the interior finish of the vehicle, this may ultimately cause injury to the driver when the airbag deploys. The rapid timing required to inflate an airbag before a person has struck a surface in the vehicle (such as the windshield) requires that the airbags open with explosive force. This will not typically injure a user situated normally in the vehicle, but body parts resting too close to the airbag, such as arms and hands, will be subject to the explosive force of the airbag's deployment. A user could then suffer serious injuries when the airbag deploys.
Even when known seams is not visible, they may be easily discovered by a user by simply pressing on the outer layer or cosmetic surface. In either case, if a linear seam is used behind the outer layer or cosmetic surface, the pressure causes the cover to fold inward along the seam, so that the seam is readily perceptible. Repeated application of pressure may even break the seam. Even if a seam is not otherwise visible, it is preferable, for many reasons, to ensure that it is entirely hidden from a user until the airbag deploys.
Accordingly, a need exists for a safety restraint device cover with a seam that will not be visible to a vehicle occupant, even when no styling line is used. The indentation produced by the seam is difficult to eradicate without the use of additional manufacturing processes to join disparate materials or alter the shape of the seam. Consequently, a need exists for a novel seam design that will not show through the outer layer, if a separate material is applied, or the cosmetic surface, if a single-shot, or single material process is used to form the cover. A need further exists for such a cover that is manufacturable through inexpensive processes such as stamping or molding.